The melting point is the temperature at which a substance can melt and change into a liquid without any further heating. The temperature at which a substance can melt depends on many factors, including the purity of the substance and the surrounding pressure.
Ionic Compounds Have High Melting Points
The ions of an ionic compound (which are charged) have very strong intermolecular attractive forces, and the force of attraction between cations and anions in an ionic compound increases with increased molecular weight. The interionic distance between the ions of an ionic compound is governed by Coulomb’s law, in which the force of attraction depends on the amount of charge and the distance between the ions.
Ionic compounds can be divided into two types: those that are solids and those that are liquids. Generally, the ions in an ionic compound are very close together in the solid state. In the liquid state, the ions are more mobile, but still very close together.
Ionic compounds have very high melting points, which can be attributed to the strong lattice energy of the ions in an ionic compound. The lattice energy of an ionic compound is related to the ionic radii of the ions. This lattice energy determines the crystal structure of the ionic compound and relates to the melting point.